DESCRIPTION (Taken from the application): Critical functions for epidermal gap junctions have been elucidated by the discovery of mutations in human connexin genes underlying palmoplantar keratodoma (PPK) and erythrokeratodermia variabilis (EKV). Mutations in the connexin26 (Cx26, or GJB2) gene are not only a major cause of nonsyndromic deafness, but can also cause syndromic forms of hearing loss that are associated with mutilating keratoderma (i.e. Vohwinkel's syndrome). In a similar fashion, mutations in Cx31 (GJB3) can cause either hearing loss, or EKV. Currently, it is not clear how two very distinct pathologies can arise from different mutations within the same connexin gene, which seems to be the case for both Cx31 and Cx26. There is evidence to suggest that simple loss of function mutations in Cx26 cause deafness, but not PPK. Thus, the Cx26 mutations which can cause both PPK and deafness must show some type of alteration of function, and the mechanisms whereby Cx26 mutation leads to pathological changes in the epidermis remains to be elucidated. Thus far, nothing is known about the functional consequences of Cx31 mutations. The objective of this application is to precisely define the functional consequences of Cx26 and Cx31 mutations that cause skin disease in humans. In addition, we seek to understand which keratinocyte functions require gap junctional communication in vivo. To achieve these goals, we first propose to analyze wildtype and mutant Cx26 and Cx31 channel behavior in the paired Xenopus oocyte assay. We will also analyze the ability of the Cx26 mutants to interact with other epidermally expressed connexins in a dominant manner. In a second specific aim, we will attempt to generate and characterize transgenic mice expressing the mutant alleles in keratinocytes in order to evaluate the in vitro derived functional differences in animal models.